Effects of Airborne Molecular Contamination on DUV Photoresists

This paper will report post-exposure delay results using Shipley UVIBISTM deep UV resist. The variables of the experiments include: processing delays (expose to post-exposure-bake and coat to exposure), different levels of ammonia, different substrates, and processing conditions. Better delay stability is observed when standing waves are reduced by processing. When standing waves are present, scumming tends to occur at the nodes; acid depletion near the nodal region prevents adequate deprotection for development to occur. The methods for detecting airborne contamination are ion mobility spectrometry for ammonia and thermal desorption gas chromatography for 1-methyl-2-pyrrolidone (NMP). Fourier transfer infrared (FFIR) spectroscopy is used to monitor the deprotection reaction of UVIIHS photoresist films with and without delays.